It has long been known that mechanical, chemical, and kinetic properties of matter are determined by the motion of atoms in the force field created by the motion of electrons. Such motion occurs on the Angstrom scale over a timescale set by vibrational motion of 10.sup.12 -10.sup.14 Hz.
Field emission microscopy (FEM) and field ion microscopy (FIM), developed in 1936 and 1951, respectively, were the first techniques to achieve nanometer-scale microscopic imaging of surfaces. These techniques employed a sharp, electrically biased tip as a highly intense source of electrons or ions. In the FEM, a large negative potential is applied to the sharp tip so that the strong field narrows the work function barrier to only a few angstroms. Electrons which tunnel through the barrier leave the tip, moving perpendicularly to the local surface; they are then accelerated onto a screen for imaging. For very sharp tips, the FEM resolution is as good as 5 Angstroms. In the FIM, the high field at a positive tip ionizes inert imaging atoms, which are accelerated to the screen. The strength of the field depends upon the position of the underlying surface atoms, enabling atomic resolution of the surface to be achieved.
The more recent development of femtosecond lasers made it possible to achieve the time resolution that enabled atomic vibrations and rotations to be followed during photochemical events. For example, see the paper by Gruebele et. al. entitled "Ultrafast Reaction Dynamics", published in Physics Today, page 24, May 1990. This was done by activating a large sample with a laser pulse and, at a precisely controlled later time, measuring with a second pulse some changing spectroscopic property related indirectly to the atomic coordinates. This method has several shortcomings: (1) it is indirect, in that it records a spectroscopic property or characteristic of the atom or molecule; (2) an atom or molecule can be optically probed only once during an entire event; and (3) a large sample must be used and signal averaging is required. No prior method known to applicant enables the recording of motion of an atom or group of atoms at the frequency of molecular vibration without signal averaging, and is capable of transmitting information as small as an atom from one location to a remote location at an ultra-high frequency.
There is a need for a method and apparatus that (1) can generate a time-dependent record of the motion of atoms directly, rather than, as in the past, indirectly, by sensing a spectroscopic property; (2) can focus on a single atom or group of atoms so that large ordered samples are not required; (3) can provide a complete record of data in real time, thereby not only obviating the need for signal averaging, but also allowing the observation of spontaneous, thermally activated events that cannot be synchronized; and (4) can transmit at high frequency to a remote location and detect information from a spot as small as a single atom.